This invention relates to a dental procedure for determining the length of the root canal of a tooth of a patient, and apparatus for use in said procedure.
In the dental treatment of a decayed tooth, it is often necessary for the dentist to known the exact length of the root canal, such length sometimes being referred to as the endodontic working length. Endodontic treatments usually involve drilling a hole through the crown of the tooth to gain access to the underlying root canal. The pulp within the canal is then removed by use of fine diameter reamers and files. The cleaning of the canal is generally referred to as biomechanical preparation; and thoroughness of such cleaning is essential for disinfection purposes and filling the canal. Prior to the preparation of the canal, the dentist must determine the exact canal length to prevent the touching or penetration of the periapical tissues by the cleaning instruments with attendant inflammation or infection.
The most commonly employed technique for measuring the endodontic working length is by inserting a metal probe into the root canal in incremental steps while taking x-ray pictures to determine the degree of penetration of the probe. Such technique exposes the patient to considerable x-ray dosage, and still risks contact with the periapical tissues or periodontal membrane of the apex of the canal.
More recently, electronic devices have been utilized wherein electrical signals emitted from an electrode inserted into the canal to a depth close to the apex are modulated by the chemical and physical characteristics of the canal. The magnitude of the modulated signal is indicative of the length of the canal. However, variable amounts of water, blood or exudate within the canal, and the presence of lateral foramina or perforations cause measurements by electronic devices to be unreliable. Also, the probe may push material within the canal against the apical area, thereby producing irritation.
Although the total apparent length of the root canal can be seen on an x-ray picture, the true length is not determinable from the x-ray picture because of the unknown orientation of the tooth with respect to the plane of the x-ray film.
It is accordingly an object of the present invention to provide a method for accurately and reliably determining endodontic working length without subjecting the patient to repeated x-ray exposure, and without risk of contacting the periapical tissue.
It is a further object of this invention to provide apparatus useful in the method of the foregoing object.
It is another object of the present invention to provide apparatus of the aforesaid nature of simple construction and amenable to easy operation by the dentist.
These objects and other objects and advantages of the invention will be apparent from the following description.